Segmented wheel and method and system for controlling a segmented wheel

ABSTRACT

An adaptable wheel has a central hub, radial segments connected to the central hub at a proximal end and extending radially from the central hub, each radial segment having a linear actuator configured to change a length of the radial segment; a shoe connected to a distal end of the radial segment for contacting a surface being traversed by the wheel; and a locking mechanism for selectively preventing linear motion of the linear actuator. A control system for an adaptable wheel includes a distance sensor on a vehicle for determining distance to a surface in the path of the vehicle and a computer for receiving distance information from the distance sensor and, responsive to the distance information, determine a desired length of a segment of an adaptable wheel for maintaining a hub of a wheel level, and provide control signals to a linear actuator of the segment.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of copending U.S.patent application Ser. No. 14/214,109 entitled SEGMENTED WHEEL ANDMETHOD AND SYSTEM FOR CONTROLLING A SEGMENTED WHEEL, filed Mar. 14,2014, which issued on Jan. 30, 2018 as U.S. Pat. No. 9,878,576, whichclaims priority under 35 U.S.C. § 119(e) to U.S. Provisional PatentApplication Ser. No. 61/787,400 entitled SEGMENTED WHEEL AND METHOD ANDSYSTEM FOR CONTROLLING A SEGMENTED WHEEL, filed on Mar. 15, 2013, thesubject matter of which are incorporated by reference herein in theirentirety and for all purposes.

FIELD OF THE INVENTION

This application relates to vehicle wheels.

BACKGROUND OF THE INVENTION

Rough or irregular terrains pose difficulties for vehicles attempting totraverse such terrain. This is particularly true for robotic vehicles,and indeed robotic vehicles may frequently be called upon to traverserough or irregular terrain. Various attempts have been made to alleviatethese difficulties, including spring/damper and active suspensions,hovercraft, and reciprocating leg mechanisms. However, these solutionssuffer from a number of disadvantages. They variously tend be large andenergy inefficient, expensive, generate noise and suffer limitations inspeed, effectiveness and load bearing capabilities.

Circular wheels are attached at their center to a hub or axle attachedto the frame of a vehicle through a suspension assembly. As the surfaceof the wheel contacts the surface over which the vehicle is traveling,the entire wheel rises or falls with the profile of the terrain surface.To prevent such non-rotational motion of the wheel from beingtransferred to the frame of the vehicle, the suspension assembly employssprings, shock absorbers or struts to absorb some of the force appliedthrough the non-rotational movement of the wheel. These suspensionsystems are reactionary and adjust only after the wheel has changed itsposition relative to the vehicle frame. The suspension does not absorball of the force of the wheel's motion and some of the energy applied bythe force of the upward or downward motion of the wheel is transferredto the vehicle and its occupants.

A wheel system that addresses one or more of these disadvantages and/oris proactive and adjustable to provide a smooth ride would bebeneficial.

SUMMARY

An adaptable wheel comprises a central hub, and radial segmentsconnected to the central hub at a proximal end and extending radiallyfrom the central hub. Each radial segment includes a linear actuatorconfigured to change a length of the radial segment. A shoe is connectedto a distal end of the radial segment for contacting a surface beingtraversed by the wheel. A locking mechanism is configured to selectivelyprevent linear motion of the linear actuator. A control system for theadaptable wheel includes a distance sensor for determining distance to asurface in the path of the vehicle and a computer processor forreceiving distance information from the distance sensor and, responsiveto the distance information, determining a desired length of a segmentof the adaptable wheel for maintaining the hub of the wheel level, andproviding control signals to a linear actuator of the segment.

A computer controlled segmented wheel includes a plurality of adjustableradial segments. The first end of each radial segment is attached to acommon hub at the center of the wheel. The second end of the radialsegment includes a shoe assembly which comes into contact with theground when the associated radial segment is in a position substantiallyperpendicular to the ground's surface and below the hub of the wheel.The outer surface of the shoe is coated with a friction producingmaterial, such as rubber. As the wheel rotates about the hub, eachradial segment contacts the surface as that radial segment rotates pastthe surface. The wheel assembly is attached to the frame of a vehicle atits hub. The vehicle includes a distance sensor that is configured tosense the distance from a fixed point on the vehicle frame to a point onthe ground ahead of the vehicle in the vehicle's direction of travel. Acomputer receives information relating to the distance from the fixedpoint on the vehicle to a point on the ground in front of the vehicleand calculates a distance between the height of the hub and the groundsurface at the measured point in the surface. Based on the distancebetween the vehicle and the measured point, a radial segment isidentified which will be in contact with the ground surface at themeasured point. A distance between the hub of the wheel and the measuredpoint on the ground's surface is calculated. The computer sends anactuation control signal to a radial adjuster on the identified radialsegment to adjust the length of the radial segment to match thecalculated distance. By calculating the length of each radial segmentbased on a substantially constant distance between the hub and a pointon the ground where each radial segment will contact the ground, the hubis maintained at a consistent height throughout the length of travel.Therefore, the vehicle does not experience movement proportional to thenon-rotational movement of the wheel as the wheel is adapted to maintaina consistent height between the hub and the ground.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of a radial segment accordingto an embodiment of the present disclosure.

FIG. 2 is an elevation view of a wheel assembly comprising a pluralityof radial segments of FIG. 1 according to an embodiment of the presentdisclosure.

FIG. 3 is an elevation view of a vehicle equipped with the wheelassembly of FIG. 2 and a computer controlled distance sensing systemaccording to an embodiment of the present disclosure.

FIG. 4 is an elevation view of a radial segment showing relativedimensions of components of the segment according to an embodiment ofthe present disclosure.

FIG. 5 is a partial cross-sectional view of a radial segment accordingto another embodiment of the present disclosure.

FIG. 6 is a partial view of a simplified wheel assembly according to anembodiment of the present disclosure.

FIG. 7 is a bottom view of an exemplary shoe for use in a wheel assemblyaccording to an embodiment of the present disclosure.

FIG. 8A is a side view of an exemplary shoe for use in a wheel assemblyaccording to an embodiment of the present disclosure.

FIG. 8B is a top view of the shoe of FIG. 8A.

FIG. 9 is a top view of an exemplary partial shoe assembly according toan embodiment of the present disclosure.

DETAILED DESCRIPTION

To maintain a smooth, steady and stable ride for a wheeled vehicle as ittravels over a surface, the point at which the vehicle is coupled to thewheels must be maintained at a level height relative to a fixed altitudeon the Earth's surface (e.g. level). As the wheel contactsirregularities on the surface, the wheel is urged upward or fallsdownward. According to an embodiment of this disclosure, a wheel andassociated control system are configured to maintain a hub on which thewheel is mounted level over uneven terrain. A wheel includes a hub and aplurality of radial segments radiating outward from the hub. Each of theradial segments includes independent actuators for adjusting the segmentlength. A distance sensor detects the height of terrain toward which thewheel is moving. A computer receives the height data from the distancesensor. In response to the height data, the computer provides controlsignals to cause the actuators to adjust the segment length to maintainthe hub level as the segment encounters the terrain.

FIG. 1 is a partial cross-sectional view of an adjustable radial segment100 which may be implemented as part of a wheel and associated controlsystem. The radial segment 100 is defined generally by an actuatorassembly comprised of an outer fixed sleeve 109 and a movable spoke 105.The spoke 105 and outer sleeve 109 have the same longitudinal axis.Spoke 105 is moveable along the common longitudinal axis. The spoke 105is connected at a first end, or a distal end, of the actuator assemblyto a shoe 101. The spoke 105 is coupled to the shoe 101 by a wrist joint107 including a pin or axle. Wrist joint 107 allows the shoe 101 topivot about an axis of the axle or pin and relative to the longitudinalaxis of the actuator assembly.

Shoe 101 is a rigid body. The shoe 101 has an arcuate or convex lowersurface 103 which contacts the ground or surface as the wheel rotates.The arcuate surface 103 defines an segment of a circle defining theouter diameter of a wheel assembly (such as wheel assembly 200 of FIG.2). The length of the segment defined by the arcuate surface 103 dependson the number of radial segments 100 used to make up a wheel assembly.Any number of radial segments 100, greater than two, may be used to makeup a wheel assembly. Each arcuate surface 103 will be defined as asegment defining an angle between the ends of the segment and the centerhub of the wheel assembly, where the angle is determined according tothe formula: 360°÷(number of segments).

The convex surface 103 of shoe 101 may be covered with a layer of highfriction material such as rubber. The high friction material aids intraction. The high friction material may be is adhered directly to thearcuate surface 103. As shoe 101 is a rigid body, shoe 100 is not apneumatic tire. Therefore, a wheel having a plurality of radial segments100 is a run-flat wheel.

The radial segment 100 is adjustable in length between the first end atshoe 101 and the second, or proximal, end at the attachment point 121 tothe hub (not shown). To maintain the radial segment's 100 length whilesupporting the weight of the vehicle, a locking mechanism 111 isprovided. The locking mechanism is configured to selectively fix thelength of radial segment 100. Locking mechanism 111 may include anactuator, which actuator receives control signals from a controller orcomputer. Locking mechanism 111 may be configured to selectively fix therelative positions of outer sleeve 109 and spoke 105, thereby fixing thelength of radial segment 100. In an embodiment, locking mechanism may bemounted on and fixed in position on outer sleeve 109, and selectivelyengageable with spoke 105.

In the illustrated embodiment, locking mechanism 111 has a locking pin113 movably mounted in an aperture in the wall of outer sleeve 109. Thelocking pin 113 may be moved from a first position in which the radialsegment 100 is unlocked and a second position in which the radialsegment 100 is locked. When in an unlocked position, locking pin 113 isnot in physical contact with spoke 105; spoke 105 is free to moverelative to outer sleeve 109. In a locked position, the locking pin 113is moved to a position where the locking pin 113 contacts the spoke 105.Locking pin 113 may engage spoke 105 through an aperture or bore in thespoke 105. In the case of a spoke without apertures or bores, lockingpin 113 may be forced against the uniform outer surface of spoke 105with enough force to create friction sufficient to prevent spoke 105from sliding within outer sleeve 109. See, for example, FIG. 5, whereinlocking pin 113 comprises a free end abutting an opposing uniform outersurface 112 of spoke 105 with enough force to create friction sufficientto prevent spoke 105 from sliding within outer sleeve 109. The lockingpin 113 may be moved between a locked position and an unlocked positionby an actuator, such as a solenoid or pneumatic or hydraulicarrangement, by way of example. The actuator may be configured tooperate in response to control signals received from a connectedcontroller, such as an onboard computer.

Radial segment 100 further has a sensor for detecting a present lengthof the radial segment 100. Such a sensor may provide an output signalindicative of the present length to a system controller or onboardcomputer. A sensor for detecting a present length of the radial segment100 may be implemented by position sensor 123. Position sensor 123 isconfigured to sense the relative positions of spoke 105 and outer sleeve109. Position sensor 123 is configured to provide an output voltageproportional to the sensed position. For example, position sensor 123may be a rheostat connected to spoke 105 such that when the spoke 105moves, position sensor 123 outputs a voltage proportional to therelative position of spoke 105.

Radial segment 100 further has one or more actuators for moving spoke105 relative to outer sleeve 109. Linear actuator 115 is configured toprovide linear motion of spoke 105 relative to outer sleeve 109. Forexample, as shown in FIG. 1 by way of non-limiting example, a conductivecoil 117 wrapped around an electromagnetic core 119 may be used tocreate a solenoid which may be electrically controlled to provide linearmotion of spoke 105. In other embodiments, linear actuator 115 may be inthe form of a driven threaded interface, such as a worm gear, apneumatic piston, a hydraulic piston, or other mechanism. Linearactuator 115 may be configured to move either of spoke 105 and outersleeve 109 while holding the other fixed. Linear actuator may beconfigured to respond to control signals from a connected controller,such as an onboard computer.

FIG. 2 is a partial cross sectional elevation view of a wheel assembly200 having a plurality of the radial segments 100 of FIG. 1 according toan embodiment of the present disclosure. Wheel assembly 200 includes acentral hub 201 having a connection point 203 for coupling the wheelassembly 200 to the frame of a vehicle. Around the circumference of thehub 201, eight radial segments 100 are coupled to the hub 201 and extendradially from the hub 201 at regular angles to each other. Optionallyaccording to another embodiment, each of a plurality of radial segments100 making up a wheel may be secured to adjacent other radial segments100 through a chordal member 130. The chordal member 130 providesadditional torsional strength and stability and is attached to radialsegment 100 at points on the fixed member of linear actuator 115 (shownin FIG. 1). Chordal member 130 may be comprised of a rigid material toprovide structure integrity to the wheel. For example, chordal member130 may comprise steel, stainless steel, aluminum, magnesium, plastic,or other suitable materials. Each radial segment 100 is independentlyadjustable in length while the vehicle is in motion.

Radial segment 207 is in contact with a surface 205 on which the wheelassembly 200 is rolling. A vertical height 209 is defined between theheight of connection point 203 and a reference level 211. A controllermay provide control signals to linear actuators and locking mechanismsof wheel assembly 200 to maintain connection point 203 level as wheelassembly 200 rotates. As surface 205 is level, linear actuators ofradial segments 100 may be operated to set radial segments at a constantlength. Locking mechanisms of the radial segments may be activated tolock the lengths of the radial segments. The diameter of the wheeldefined by wheel assembly 200 may be fixed at length 213 so long assurface 205 remains level. In the present orientation, a shoe of one ofthe radial segments is in contact with surface 205. As the wheelassembly rolls, the radial segments may simply remain locked so long assurface 205 remains smooth and level.

By adjusting the length of each radial segment 100 at the point wherethe radial segment 100 is contacting surface 205, the height 209 betweenthe reference level 211 and the hub connection point 203 may be keptsubstantially constant. Substantially constant means that as the wheelassembly 200 rotates and rolls over surface 205 the path of travel ofconnection point 203 remains level to an extent where the vehicle or itsoccupants do not adversely feel the effects of traveling overirregularities in surface 205. In further exemplary embodiments, Furthercontrol schemes or algorithms may be aimed at providing inertialbalancing as wheel assembly 200 travels. Specifically, one or moreradial segments 100 opposite one or more radial segments which arecontacting the ground may be adjusted to be of equal radius or length tothose contacting the ground in order to balance wheel assembly 200 forrotational inertia forces.

Another embodiment of the present disclosure may be illustrated by thewheel assembly of FIG. 2. Each radial segment 100 is adjustable tocontrol the length between the hub 201 and the point at which the radialsegment contacts the surface 205. By controlling the length of allradial segments 100 in the wheel assembly 200 simultaneously at a chosenlength, the effective diameter 213 of the wheel assembly may becontrolled. By increasing or decreasing the effective diameter 213 ofwheel assembly 200, the distance covered by the wheel assembly 200during one full revolution of the wheel may be changed. Thus, for aconstant rotation rate of hub 201, the speed of travel of the vehiclemay be controlled by increasing or decreasing the effective diameter 213of wheel assembly 200. In this way computer adjustable wheel assembly200 may be used as a continuously variable transmission (CVT) system. Byway of example, if an onboard computer detects that the vehicle usingone of more wheel assemblies 200 has started to climb a hill, the linearactuators of the radial segments of each wheel assembly may be driven toreduce the length of the linear actuators. The reduction in lengthresults in a reduction in effective diameter of the wheel assemblies.Thus, the vehicle covers a shorter distance for the same number ofrotations of hubs 201, but applies more torque to the ground forclimbing the incline. The reduction in lengths of the radial segmentsserves as the equivalent of shifting a transmission to a lower gear.Similarly, if an onboard computer detects that the vehicle has ceased tomove uphill, and is now moving on a level surface, the computer mayprovide a control signal to the linear actuators to increase the lengthsof the radial segments. The increasing in lengths effectively increasesthe diameters of the wheel assemblies, and therefore serves as theequivalent of shifting a transmission to a higher gear. The use of oneor more wheel assemblies 200 as a CVT can provide energy savings bysaving the cost and weight of a traditional CVT transmission, as well asimprove reliability and efficiency by eliminating unreliable,power-consuming components such as belts, cones, chains, and the like.It is further noted that the force acting on the adjustable surface ofthis CVT arrangement is limited to the weight of the vehicle itself,rather than a separate apparatus that utilizes or consumers power.

FIG. 3 is an elevation view of a vehicle traversing a surface havingirregular terrain, using the wheel assembly of FIG. 2 in accordance withan embodiment of the present disclosure. The vehicle includes a chassis305 attached to a suspension frame 303 that is coupled to the hubconnection point 203 of the wheel assembly. The suspension frame 303 isconnected to the hub connection point 203 by an axle, bearing, or othermechanical coupling to allow the wheel assembly to rotate around the hubconnection point 203. Radial segments are attached to the hub.

The wheel assembly is controlled by a computer 306. Computer 306provides control signals to control the operation of linear actuatorassemblies in each radial segment 100 (shown in FIG. 1). As with theradial segment of FIG. 1, the radial segments of FIG. 3 each include alinear actuator assembly for changing the length of the radial segment.The linear actuator assembly may be configured to move spoke 105relative to outer sleeve 109 to length or shorten the length of theradial segment 207. An actuator-driven locking mechanism 111 between theouter sleeve 109 and the spoke 105 may be activated to lock the spoke105 in a given position relative to the outer sleeve 109. The linearactuator assemblies and actuator-driven locking mechanisms may receivecontrol signals from computer 306.

The actuator assembly allows the overall length of each radial segment100 to be selectable. The length of the radial segment may be controlledsuch that at the time that a given radial segment (e.g. 207) comes intocontact with the surface 301, the length of the overall radial segment207 establishes the vertical distance 209 between the hub connectionpoint 203 and a reference level 211. As radial segment 207 is in contactwith surface 301, locking mechanism 111 has, in response to controlsignals from computer 306, locked the length of radial segment 207. Thevertical distance 209 is maintained substantially constant as eachsubsequent radial segments 100 rotate into position where they makecontact with surface 301.

The vehicle of FIG. 3 has a distance detection sensor 307. Distancedetection sensor is configured to determine a distance from the vehicleto a surface in the immediate path of the vehicle in the direction oftravel. The distance detection sensor is mounted on the vehicle with adirect line of sight to a surface in the immediate path of the vehicle.The distance detection sensor 307 emits a distance sensing signal 315,319, 323 directed toward the surface 301. The signals are aimed atvarious angles and encounter the surface at points 317, 321, 325. Thesignals may be ultrasonic distance detecting signals, and the distancedetection sensor may have receivers configured to detect a time offlight and calculate the distance to an object from which the signalsare reflected, by way of example. Sensor 307 may emit ultrasonic pulsesat a variety of angles, and determine distances to the ground associatedwith angle data. Sensor 307 may provide determined distance and angledata as inputs 309 to computer 306.

Computer 306 may include a processor, such as a computer processor, indata communication with a memory device for processing data relating tothe determination of the height of surfaces in the path of travel andresponsive control of the wheel assembly. Upon receiving inputs 309containing and angle and distance information from sensor 307, computer,using vehicle speed data, and data concerning the current length of theradial segments, determines which radial segment 100 of the wheelassembly will be contacting the surface 301 at points in its path oftravel 317, 321, 325. The vertical distance between level reference 211and the points 317, 321, 325 may be determined. The vertical distance209 is used as a baseline to compute the proper length of the determinedradial segment 100, so that when the radial segment 100 contacts thedistance point 317, 321, 325 at the elevation of the reference point onthe surface 301, the height of radial segment 100 supports the hubconnection point 203 at a substantially constant vertical distance 209from the reference level 211.

Computer 306 outputs actuator control signals 311 which are transmittedto the actuator controls on wheel assembly 200. The actuator controlsignals 311 may be transmitted through cables or wires to rotaryconnectors at the hub of wheel assembly 200, or alternatively theactuator control signals may be provided to the radial segments by awireless signal transmitted from a transmitter at the computer 306, suchas a radiofrequency (RF) transmitter, and received at the radial segmentby a compatible receiver. The actuator receives the actuator controlsignal 311. In response, the actuator causes the actuator assembly tolinearly move spoke 105 to a new position relative to outer sleeve 109.The new position may be such that the overall length of the radialsegment 100 matches a value determined by the computer. A positionsensor 123 (shown in FIG. 1) may be configured to detect the position ofspoke 105 in relation to outer sleeve 109. For example, position sensor123 may be a rheostat connected to spoke 105 such that when the spoke105 moves, position sensor 123 outputs a voltage proportional to therelative position of spoke. This voltage may be returned to computer306. When the computer determines, based on the signal from the positionsensor, that the spoke 105 is in a position corresponding to adetermined target length of the radial segment. the computer may send asignal for the linear actuator to stop, and send a signal to lockingmechanism 111 to lock the spoke 105.

As the wheel assembly rotates and a locked 333 radial segment breakscontact with the ground due to the wheel's rotation, the computer mayprovide an unlock signal to locking mechanism 111 to unlock 330 spoke105. When unlocked, the spoke is free to move relative to outer sleeve109 responsive to the linear actuator. The computer may calculatedesired lengths of each segment, and successively provide controlsignals to cause linear actuators to move each segment to the desiredlength, and provide a locking signal. The moving and locking may occurafter the computer has detected that the foot of the radial arm is nolonger in contact with the surface and before the foot next contacts thesurface. It should be noted that while the radial segment 100 is beingadjusted 331, the radial segment is not supporting the weight of thevehicle because the radial segment is not in contact with the surface301. Thus, no force is being applied to the radial segment, and themovement of the spoke 105 is unencumbered by any outside force. For thisreason, little energy is needed to operate the linear actuator.

For example, distance sensor 307 detects the distance between distancesensor 307 and a point on surface 301, denoted as 327. There is a slightelevation in the surface 301 at point 327. The distance information issent by distance sensor 307 as input 309 to computer 306. Computer 306calculates, from the distance to point 327, the speed of the wheelassembly, which of the radial segments 100 will contact the surface 301at point 327. An actuator control signal 311 is sent to the identifiedradial segment to adjust its length to the proper length 329 calculatedby computer 306. As the wheel rotates near, but not to, the point wherethe radial segment contacts the ground, the actuator completes itsadjustment of the length 329. The computer then causes the lockingmechanism to lock the radial segment prior to contact with the ground orsurface. When radial segment with length 329 contacts point 327 onsurface 301, the vertical height of the hub connection point 203 will beat a substantially constant height 209. The elevation of the surface 301at point 325 is compensated for by the distance sensor's 307measurement, the computer's 306 calculation of the proper radial segmentlength 329, and the computer's control signals to adjust the length ofthe radial segments. The segment adjustment process is repeated for eachsuccessive radial segment as it rotates about the hub connection point203. Thus, at each contact point with the surface 301, the hubconnection point 203 is at a substantially constant height providing astabilized path height 335. On uneven terrain, the length of each radialsegment may be adjusted in each rotation of the wheel assembly.

The above-described system may be used for adjusting long-term height ofa vehicle. That is, if the grade of terrain being traversed is risingand/or dropping, spoke or radial segment length requires control toallow the hub to gradually shift vertically. In an embodiment, this maybe achieved by a distance sensor 307 that detects the coming terrainheight immediately ahead of the wheel assembly. In other embodiments, inorder to better accommodate grade changes, distance sensor 307 maycomprise multiple distinct distance sensors, with at least oneadditional long distance sensor configured to detect the ground surfacefurther ahead of the wheel assembly (relative to that detected by theabove-described distance sensor) for identifying long term terrain gradeslope changes. When this so-called long-distance sensor detects a changein the slope of the terrain ahead of the wheel assembly, it isconfigured to generate a control input that causes the spokes tosmoothly and gradually allow their radii to adjust. In this way, the hubmay be controlled so as to gradually rise or drop in accordance with thelong-term grade of the terrain. Moreover, in order to ensure that thehub distance from the terrain stays within the minimum and maximum(min-max) extension of the spokes, the sensor system is configured toallow the wheel to begin adjusting height predictively, before the gradeactually changes, and continuing to adjust after it has changed, thusfurther smoothing out the abruptness of such changes, as compared totraditional reactive suspension systems.

FIG. 4 is an elevation view of an embodiment of a radial segment showingrelative dimensions of components. Radial segment 100 is shown as asingle telescoping element comprised of sleeve 109 and spoke 105. A shoe101 is connected to an end of spoke 105. The other end of spoke 105 isinserted into the internal volume of sleeve 109 and is linearly moveablein relation to the sleeve 109. The distance between the center of hub411 and the end of spoke 105 defines the midpoint outer radius (R_(m))405. R_(m) 405 defines the radius of the wheel when spokes 105 are intheir midpoint extended position. In other words, R_(m) represents halfthe nominal diameter of the wheel, or the nominal outer radius of thewheel. The hub radius (R_(h)) 413 is defined as the distance between thecenter of the hub 411 and a point on the outer circumference of the hub.A travel limit (limit_(t)) represents the amount travel distance thespoke 105 can travel within the interior volume of the sleeve 109.limit_(t) may have a value between 0.00 and 1.00. A value of 0.00 wouldspecify no movement, or in other words, a fixed length radial segment. Avalue of 1.00 would indicate no overlap between the telescoping segmentsformed by spoke 105 and the sleeve 109. This would result in struc turalinstability where the spoke 105 is fully extended. By way ofnon-limiting example, a reasonable value for limit_(t) would be 0.85,which would allow 85% of the length of the interior volume of sleeve 109for linear travel of spoke 105. The remaining 15% would representoverlap of the segments to provide structural stability.

The sleeve length (length_(sleeve)) 401 may then be defined by therelationship:

$\begin{matrix}{{length}_{sleeve} = \frac{R_{m} - R_{h}}{\left( {2.00 - {limit}_{t}} \right) + \left( {0.5*{limit}_{t}} \right)}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

The spoke length (length_(spoke)) 407 is the length of the adjustablespoke-segment and is defined by:length_(spoke)=(2.0−limit_(t))*length_(sleeve)  Equation (2)

The distance from the hub 411 of the wheel to the second end of spoke105 when at mid-position is the spoke radius (R_(s)) 403 and may bedefined as:R _(s) =R _(h)+(0.5*length_(sleeve))  Equation (3)

Using the above equations, the dimensions for the sleeve 109 and spoke105 for a radial segment 100 may be calculated for any desired midpointRadius (R_(m)) 405.

For example, for a wheel having the dimensions:

-   -   R_(m)=0.5 meter;    -   R_(h)=0.05 meter; and    -   limit_(t)=0.85; the following dimensions may be calculated:    -   length_(sleeve)=0.2857 meter;    -   length_(spoke)=0.3286 meter;    -   and R_(s)=0.1929 meter.

The above calculations result in optimal dimensions for the sleeve 109and spoke 105 in the sense that they provide an adjustable radius thatis maximally variable as compared to its mid-point outer radius. Whileit should be understood that other relative dimensions could be used,they would result in reduced radial variable as a function of themid-point outer radius value. Furthermore, while the examples are shownfrom the perspective of a single element telescoping structure, theformulas may be adapted by one of ordinary skill in the art to apply toradial segments having a larger number of telescoping segments.

Where used in this description, the term processor or computer mayinclude computer processors that may be implemented in hardware,software or a combination of both. For example, some modules may beimplemented in hardware and other modules implemented in software in anycombination. Software may be stored in the form of instructions thatwhen executed by a processor, cause the processor to perform certainprocessing steps. The processing steps may include use of one or morealgorithms disclosed in this patent application to calculate values. Thesoftware instructions may be stored on a non-transitory computerreadable medium. The computer readable medium, for example, may be aflash memory, random access memory (RAM), read only memory (ROM), anoptical disk, magnetic disk or other form factor of memory suitable forstoring said instructions. The processor may be in communication withthe memory and receive instructions or processing data from the memory.Similarly, the processor may store intermediate processing data orresults in the memory. This data may be available for later retrieval bythe processor or by other components of a given system incorporating theprocessor and memory.

FIG. 5 illustrates a wheel assembly 100 having features similar to thosedescribed above with respect to FIG. 1, with like numerals representinglike features. Specifically, in some embodiments, locking mechanism 111includes locking pin 113 having a free end surface configured to abut anelongated, uniform (i.e. continuous or straight) opposing surface 112 ofspoke 105 with sufficient force such that spoke 105 may be secured inthe illustrated position only by friction force generated between theseopposing surfaces (as distinct from shear forces on pin 113 in theembodiment of FIG. 1). By not engaging with apertures formed in spoke105 (see FIG. 1), pin 113 of locking mechanism 111 may engage with spoke105 at nearly any desired position along the length of surface 112 ofspoke 105, while not being limited by a minimum spacing requirementbetween apertures. In this way, the illustrated embodiment provides muchfiner operational control of wheel assembly 100.

Still referring to FIG. 5, a resistive element 114 may also be providedand configured to either lock the orientation of shoe 101 relative tospoke 105 about wrist joint 107, or provide a resistance to the rotationof shoe 101 about wrist joint 107. In embodiments, resistive element 114may take the form of a clutch, such as a computer-controlled clutch, ora translatable pin-based locking mechanism having features similar tolocking mechanism 111, for selectively fixing the position of shoe 101relative to spoke 105. Resistive element 14 may take the form of one ormore elastic elements, such as a torsion spring or rubber bushing, forresisting rotation of shoe 101 in either direction about wrist joint 107relative to a neutral, central position illustrated in FIGS. 1 and 5.Fixing, or resisting movement of, the position of shoe 101 when the shoecontacts (or just prior to contact with) the ground ensures that nopower loss occurs as the wheel engages with the ground. This arrangementfurther resists slipping of the shoe during ground-contact from thetangential wheel torques due to accelerations and decelerations of thevehicle. Moreover, by selective controlling and/or fixing the positionof shoes 101 about wrist pin 107 (e.g. by a control signal generated bycomputer 306 operatively coupled to a locking mechanism), smoothtransitions between spokes as they transfer between bearing weightduring rotation may be realized.

Referring now to FIG. 6, another embodiment of a wheel assembly 600according to the present disclosure is shown. Wheel assembly 600 (only aportion of which is illustrated) includes radially-moveable spokes 602which may comprise features similar to those set forth above withrespect to FIGS. 1-5. Wheel assembly 600 further comprises a pluralityof shoes 604,605. Specifically, in the illustrated portion of wheelassembly 600, pairs of shoes 604,605 are arranged generally between eachpair of adjacent spokes 602. Each pair of shoes 604,605 may alsoreferred to as a single shoe comprising two sub-shoes 604,605.

Each pair of shoes 604,605, or sub-shoes, may be pivotally connectedtogether. Specifically, each pair of shoes 604,605 may be pivotallyconnected at a joint 620 arranged intermediate (or generally betweenends of) each pair of spokes 602. Likewise, adjacent shoes 604,605arranged on either side of a given spoke 602 may be pivotally connectedto one another, as well as pivotally connected to the spoke, at a joint630. In this way, in aggregate, shoes 604,605 may define a chain orseries of pivotally connected shoes or sub-shoes. With each spoke 602 ofwheel assembly 600 arranged at a common length (e.g., arranged in afully retracted position), this series of shoes may define a generallyuniform circle 680.

Shoes 604,605 further comprise respective contact surfaces 606,607,which may be configured to at least partially overlap one another whenthe wheel assembly defines generally uniform circle 680. Morespecifically, and referring generally to the bottom view of two shoes604,605 as shown in FIG. 7, contact surfaces 606,607 of shoes 604,605may define interdigitated or overlapping fingers. In other embodiments,contact surfaces 606,607 of shoes 604,605 may be configured only to abutone another in this radial position, or may be configured to define agap therebetween, without departing from the scope of the presentdisclosure.

Referring again to FIG. 6, joints 620,630 may comprise pins 610 arrangedthrough apertures 615 formed through each shoe 604,605. In oneembodiment, each aperture 615 comprises a slotted opening. In otherembodiments, only one of the apertures of a pair of joined shoes 604,605is slotted, with the other comprising a circular opening, for example.The use of slotted apertures 615 enables joints 620,630 to permit boththe rotation of shoes 604,605 relative to one another, as well as lineartranslation therebetween. In this way, joints 620,630 define bothpivotable and slideable connections for accommodating differing lengthsof adjacent spokes (as illustrated in FIG. 6), as well as to permit moreflexibility and movement of shoes 604,605 when wheel assembly 600 istraversing uneven terrain.

In the embodiment of FIG. 6, the angle of shoes 604,605 relative tospokes 602 may be controlled by altering the relative lengths ofadjacent spokes 602. Moreover, as set forth above with respect to FIG.5, independent control mechanisms (e.g., computer controlled clutchesassociated with joints 630) may also be implemented to enable smoothtransition between spokes as they transfer between bearing weight duringrotation. In particular, the position of the shoe may be locked justprior to contacting the ground. The embodiment of FIG. 6 also furtherfacilitates nearly constant wheel-hub altitude (or height relative aconstant reference frame) as weight transfers between spokes.

Referring now to FIGS. 8A, 8B and 9, more detailed views of exemplaryshoes (e.g., shoe 604 and/or 605) are provided. Referring generally toFIGS. 8A and 8B, exemplary shoe 604 includes a monolithic body 612having slotted apertures 615 formed therethrough. Body 612 furtherdefines contact surfaces 606 protruding therefrom. Apertures 615 alongwith pins 610 arranged therein, define joints 620,630 between adjacentshoes as illustrated in FIG. 6. Pins 610 may further include heads 611on either end thereof. One or more springs 640 (e.g., coil springs) maybe attached to each pin 610 (e.g., via heads 611) on a first endthereof, and attached to body 612 on a second end thereof. Springs 640are configured to resist rotation of pins 610, as well as to restraintheir linear motion within apertures 615. Exemplary springs 640 may bereplaced with other elastic or friction-based arrangements (e.g.,elastic bushings, torsion springs, etc.), as set forth above withrespect to FIG. 5, without departing from the scope of the presentdisclosure. As shown in FIG. 8B, body 612 of shoe 604 may define arecess 650 on a first end thereof and a protrusion 660 on a second endthereof through which apertures 615 are formed. Recess 650 is configuredto receive a similar protrusion of an adjacent shoe, while protrusion660 is configured to engage with a recess of another adjacent shoe.

Referring generally to FIG. 9, in an alternate embodiment, shoe 604comprises features-similar to those set forth above with respect toFIGS. 8A and 8B, including slotted apertures 615, springs 640 and pins610. However, as illustrated, pins 610 extend through clevis-likeportions of adjacent shoes 905, with the first ends of springs 640attached thereto. Springs 640 are configured to bias pins 610 centrallywithin apertures 615, as well as to resist relative rotation betweenshoes 604 and 905. Accordingly, in the exemplary embodiment, only shoe604 comprises slotted apertures 615, with adjacent shoes either fixedlyattaching to pins 610, or accepting pins 610 via circular apertures.

While the foregoing invention has been described with reference to theabove-described embodiment, various modifications and changes can bemade without departing from the spirit of the invention. Accordingly,all such modifications and changes are considered to be within the scopeof the appended claims. Accordingly, the specification and the drawingsare to be regarded in an illustrative rather than a restrictive sense.The accompanying drawings that form a part hereof, show by way ofillustration, and not of limitation, specific embodiments in which thesubject matter may be practiced. The embodiments illustrated aredescribed in sufficient detail to enable those skilled in the art topractice the teachings disclosed herein. Other embodiments may beutilized and derived therefrom, such that structural and logicalsubstitutions and changes may be made without departing from the scopeof this disclosure. This detailed description, therefore, is not to betaken in a limiting sense, and the scope of various embodiments isdefined only by the appended claims, along with the full range ofequivalents to which such claims are entitled.

Such embodiments of the inventive subject matter may be referred toherein, individually and/or collectively, by the term “invention” merelyfor convenience and without intending to voluntarily limit the scope ofthis application to any single invention or inventive concept if morethan one is in fact disclosed. Thus, although specific embodiments havebeen illustrated and described herein, it should be appreciated that anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations of variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

What is claimed is:
 1. An adaptable wheel comprising: a central hub; aplurality of radial segments connected to the central hub at a proximalend and extending radially from the central hub, each radial segmentcomprising a linear actuator having a fixed portion and a spoke movablewith respect to the fixed portion, the linear actuator configured tochange a length of the radial segment in response to a first controlsignal; a plurality of shoes, wherein each of the plurality of shoes isrotatably connected to an end of one of the spokes and configured tocontact a surface being traversed by the wheel, and a resistive elementconfigured to resist rotation of the shoe from a first angularorientation relative to the spoke, wherein the resistive elementcomprises a locking mechanism configured to selectively lock theposition of the shoe relative to the spoke in response to a secondcontrol signal.
 2. An adaptable wheel comprising: a central hub; aplurality of radial segments connected to the central hub at a proximalend and extending radially from the central hub, each radial segmentcomprising a linear actuator having a fixed portion and a spoke movablewith respect to the fixed portion, the linear actuator configured tochange a length of the radial segment in response to a first controlsignal; and a plurality of shoes, wherein each of the plurality of shoesis rotatably connected to an end of one of the spokes and configured tocontact a surface being traversed by the wheel, wherein first and secondshoes of the plurality of shoes are arranged between first and secondadjacent radial segments of the plurality of radial segments, the firstshoe comprising a first end rotatably coupled to an end of the spoke ofthe first radial segment and a second end rotatably coupled to a firstend of the second shoe; the second shoe comprising a second endrotatably coupled to an end of the spoke of the second radial segment;and wherein third and fourth shoes of the plurality of shoes arearranged between the second radial segment and a third radial segmentadjacent to the second radial segment.
 3. The adaptable wheel of claim2, wherein: the third shoe comprises a first end rotatably coupled to anend of the spoke of the second radial segment and rotatably coupled tothe second end of the second shoe, and a second end rotatably coupled toa first end of the fourth shoe; and the fourth shoe comprises a secondend rotatably coupled to an end of the spoke of the third radialsegment.
 4. The adaptable wheel of claim 3, wherein: the second shoe isslideably coupled to the end of the spoke of the second radial segment;and the third shoe is slideably coupled to the end of the spoke of thesecond radial segment.
 5. The adaptable wheel of claim 4, wherein thesecond shoe is slideably coupled to the third shoe.
 6. The adaptablewheel of claim 4, wherein the second shoe is slideably coupled to theend of the spoke of the second radial segment.
 7. A vehicle wheelsystem, comprising: a plurality of segmented wheels, each wheelcomprising: a central hub; a plurality of radial segments connected tothe central hub at a proximal end and extending radially from thecentral hub, each radial segment comprising a linear actuator havingmoveable spoke, the linear actuator configured to change a length of theradial segment in response to a first control signal; and a plurality ofshoes, wherein each of the plurality of shoes is rotatably connected toan end of one of the spokes and configured to contact a surface beingtraversed by the wheel; a computer processor configured to calculate atarget radial segment length and generate the first control signalindicative of the target radial segment length, and a locking mechanismconfigured to selectively lock the position of the shoe relative to thespoke in response to a second control signal generated by the computerprocessor.